Blanching at night of denervated bands in teleostean tail fins is due to pigment aggregation in melanophores by melatonin

Abstract

1. 1. During our studies on the Nile tilapia, Oreochromis niloticus, and the gluttonous goby, Chasmichthys gulosus, we noticed that dark denervated bands on the fins turned pale at night. 2. 2. Even in the daytime, the blanching of such bands could be induced by placing the fish in the dark. 3. 3. Pinealectomy suppressed the reversal in colouration of the bands. 4. 4. An injection of melatonin gave rise to the reversal in the daytime. 5. 5. Denervated melanophores exhibited hypersensitization to melatonin. 6. 6. It appears that an elevated nocturnal titer of the pineal hormone, melatonin, brings about the aggregation of pigment in the hypersensitized melanophores, which in turn leads to the blanching of the denervated bands. © 1991.